Drafting machine



April-17, 1945'. L. KETTING I 2,374,020.

DRAFTING MACHINE Filed June 12, 1941 IN VENTOR BY LEENDERT KETT\NG.

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ATTORNEYS Patented Apr. 17, 1945 IDEAFTING MACHINE-151.5. 1.

: Lcendert Ketting,

Secaucus, NJ as sigrio'r v j ,Keufflj z Esser Company, HobokenyN, J., =a 'corporation-cf liew Jerse v wiionliunej zi 1941; Sean; 391.665 f; l

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. C ms This invention relates to parallel motion dratting devices rOf the kind in which the several tools the :draftsman handles most frequently are em-.- bodied .in principle in one unit *130 obviate thenccessity of the draftsma-n reaching about. for a required tool. thereby enabling thewdraftsma'n to keep his attention concentrated directly upon the drawing. Drafting devices of this character have heretofore been proposed in whichadjacent ends of two arms are pivoted together, the tree.

end of acne :arm being-secured to the. remote side of the drafting board while thefree end of the.

other .arm is provided-with ahead comprising a ,protractor and straight-edges which are'in :fixed angular relation to move about the center of the protracto-r :as an axis. Such drafting machines have been of two general kinds-cneof which-com- Still-anotherhbgiect ofthe-inven-ti'on is to ad just the counterr-halancin-gImeansiv Inccarryingk-the-Linvention into eflect, tensioning mean'svis provided which extends between an arm :and an angularly movable member.

These andother obj ects of the inventiontand theamean's for their attainment will be more;ap.- parent :from117he lfollowingqcletailed description,

taken ;in--.c.onnection Withm-bhe accompanying prises parallel motion mechanism in the form of a Jointed arm composed of two parallelograms. In another form, the arms have pulleys, spaced apart thereonwith flexible d-ri-vingW-meansbetween the pulleys, one pulley at the joint lie-- tween the two arms being common to the-flexible driving means or tension members, :such as belts, oihotharms. 7 y

Drafting devices of this character "are fre- 'quently used upon drafting boards which are inclined at an angle to the horizontal. Since the arms of the drafting machine have considerable weight and the head at the free end of the articulated arm is also :of considerable weight, there is frequently a tendency toward accidental movement due to forcesyof gravity when the arms are positioned .on one side or the other .of a vertical plane passing through the anchor andperpendicular to the remote edge of the board; Manyattempts have been made .to counterbalance the weight ofthe arms to thereby prevent their accidental displacement.

. :Oneob-ject of the present invention is countere hala-ncingmeans for the weight of the-arms, which maybe readily contained within an Another object of the invention'iscounterbalancing means, the effect of which is applied directly to :the :ang-ularly movable members or supports which are relatively angular-1y movable with respect to the frame of the arm and about which the flexible driving means pass and .be-

tween which nect. I

A further :object of the invention is counterbaiancing means which will not interfere with the =adtiustment of the fixed pulley by which the proper angularity of the .straighteedges is orig-inallyset-toaibaseline. ,i r

they extendand drivingly intercondrawing illustrating one embodiment by which the invention may 'beirealized -and in which: e .li ijeure- 1-1 a viewshow-ing aedrafting machine mounted'onra draftingrtable;-=a.

Figure '2 ,is :a view .on 'anenlarged scale of the oounterbalancing means, the upper portion of the casing being removed to show detail of constructiomand Rig-111KB 3 is a vertical" sectional view taken in the planes .indicated by thehroken lines -3- 3 of Figure .2 and-lookingu-in thedirection of the arrows.

. I :Bef-erhing there is illustrated Eigure llza typical gendless band type of drafting machinewhich ,includesta pair of arms or struts 6,; 1,}bachof whiohis constnucted to include an end .memberat each of its ends held apart by tubes- 8, .8 extending into the and members and I thrdughwhiehthe iendless lbands lll pass. The, I upper ,armMBJncIudesa pivot 'endmember I2 I which is pivotally mounted on the ianc hor ,I 4 and at .the other -end,a .pivotend member :16 which in turn .c arri es'fthe, ,pivot .end member l8 of the-socalled -lowrfarm =l. Y .Thegendmember 20 at the free end of lthe. arm 1,. carries the head .27.v -.on

which are mounted the; straight edges 24. In the illustratedl,embodiinent, the l anchor I! 4 comprises a rram da tea to engage. thedrawing table 25 and be'iclamped .thereto by the clamp screw ,28. The bracket consists of a flat surface inembertfl, Figure v3, to-rest .on the. topfaceof the drawing board and with a d nwa d y.de endin rositioning wall .32 lying in .--a :Dlane at right angles to the ssurtace anemberidso that it can; be placed on :a drawing board-and vfit, against the sidevw 'h relative accuracy. bracket is formed at its lowermost portion with threaded bosses 34 though which pas the clamp screws .28 by which thebracket/mayibe -.rigidly--mounted on the drawing'eboargleor. :drawing .-ttable whichis firmly clamped between the surface 'member :30 and the headsoT the clampscrews; Above. the table memberi-llies two spacedbearing members 31 to which are pivotally mounted th'eadjustableplate =33 which pivotally supports the upper end. of the arm pplate 3agfisza bifurcatedmember having spaced arms 38 provided with pivots 29 mounted in the two spaced bearings 31. The plate 33 is formed on the side remote from the pivots with a tubular portion 46 within which is rotatably mounted a sleeve 4| carrying the pulley 36 on its upper end. 'Ihepulley 36 rests on the tubular portion 46 of the frame or plate 33. The sleeve 4| is adjustable radially to adjust the pulley and band ID. in arm 6, as will be understood. Thi is accomplished by securing an arm 45 to the lower end of the pulley sleeve 4|. The free end of arm 45'is formed with an arcuate slot 41 receiving a bolt 49 mounted in the frame. Upon loosening the bolt 49 by means of the handle 50, the arm may be moved as desired to adjust the pulley in orientation with respect to the anchoring means and then looked in adjusted position.

The arm 6 is free to turn about a pivot pin 52 journalled within bearings 53 mounted inside the pulley sleeve 4|. The pivot pin 52 is held against accidental removal by a locking screw 54 bearing against the lower bearing 53.

To counterbalance the weight of the arms, counterbalancing device is disposed within the upper end member of the respective arms. In the illustrated embodiment, only the counterbalance of arm 6 is shown but it will be understood that the pertinent structure therein is illustrative of structure which may be incorporated in both arms. Briefly described, the counterbalancing device comprises an eccentric on thepulley about which a strap from the arm extends, the strap including a tensioning device. As shown, a disc 56 is mounted eccentrically on the pulley 36. The disc 56 is formed, preferably on one diameter, with an elliptical aperture 58 permitting the passage of the pivot pin 52 and the socket portion 5| in which the pivot pin 52 is mounted in the arm member l2. The aperture 58 is sufllciently oversize ior this purpose in all positions of adjustment of the disc 56. As shown, the disc 56 is adjustably mounted on the pulley 36. To this end, the disc 56 is formed with slots 60 through which screws 62 pass through arcuate slots 65 in the pulley 36 intothe relatively fixed tubular portion 40 of the plate 33. The axes of the slots are preferably parallel to the major axis of the elliptical opening 58. Bushings 64 are shown'as mounted -on the screws 62 to support the disc above the surface of the pulley.

Surrounding the eccentric disc 56 is a strap shown as a circular frame member or ring :66 provided with a radially extending arm' 61 formed at its end with spaced downwardly extending ears 68. The strap member 66 is made freely rotatable about the eccentric member 56 by providing the opposing edges of the two members with raceways I6 containing anti-friction members, such as the balls I2.

Across the open end of the end member is a frame member I4 apertured as at l6, 16 for the passage of the tubes 8 and by which'the end 14 is fixed against displacement. The member l4 serves as an abutment to which is secured one end (a; as-tension device to which is secured the strap The tension device is composed of twospaced frame members 18 and 19, each provided with three spaced apertures. A bolt 8| passes through an aperture 82 in the fixed frame member I4 and passes through both frame members I8 and I9 and is threaded into a nut 83 on the side of the member I9 nearest the pulley 36. It is thus fixed to the frame member nearest the pulley 36. This nut has an arm 85 extending beneath the frame member 19 to prevent the nut 83 from turning. Bolts 81 extend through the apertures in both frame members '16, 19 on each side of the apertures for bolt 8|. Bolts 81 are secured in the respective ears 68 and their heads are on the side of the frame member 18 most remote from pulley 36. Compression springs 89 encircle each of the bolts 81 and 8| between the frame members 16 and I9 to urge the frame members away from one another. The compression springs are placed under the desired torsion by rotating the bolt 8| and to this end, a wing nut-like head is mounted on the bolt 8| on the outside of the frame member 14. Thus as the bolt 8| is rotated, the frame members 18 and I9 are drawn together until the proper degree of tension is placed upon the frame members 66, 61.

As viewed in Figure 2, the normal tendency of the arm 6 is to rotate, due to the weight of the arms and head, in a counter-clockwise direction about the axis of the pivot pin 52. Since the disc 56 is eccentric with respect to the pivot pin 52 and pulley thereon, as the arm tends to swing in a counter-clockwise direction, the distance between the frame 14 and the eccentric disc increases thereby placing compression upon the compression springs. In resisting the compression, the springs oppose the tendency of the arm to rotate in a counter-clockwise direction. At the same time the arm may be normally moved to any position on the drawing board against the ac- Y tion of the springs. By suitable selection of the springsand correctly positioning the eccentric disc and placing the springs under the requisite compression, the tension on the arms may be adjusted to counterbalance the weight of the arms. It 'will be readily appreciated that the same counterbalancing device may be provided, if found desirable, in the end member IS on arm 1 although in many situations, this may not be found necessary in view of the fact that the nor mal actionof the belts and pulleys restrained by the counterbalance in the upper arm may be sumcient for the purpose at hand.

Various modifications will occur to those skilled in the art in the composition, configuration anddisposition of the various component elements going to make up the invention as a whole and particularly the composition of the compressible members and the manner in which the strap is affixed and formed and no limitation is intended by the phraseology oi the foregoing specification or illustrations in the accompanying drawingexcept as indicated in the appended claims.

What is claimed is:

1. A parallel motion drafting device of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, one of said arms being pivoted at a free end to the anchoring means, a pair of spaced pulleys in each arm, an endless band passing around each pair of pulleys, eccentric means carried by a pulley, a strap around the eccentric means and tension means one end of which is connected to the arm and the other end of which is connected to the strap.

2. A parallel motion drafting device of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, one of said arms being pivoted at a free end to the anchoring means, a pair of spaced pulleys in each arm, an endless band passing around each pair of pulleys,-a disc eccentrically mounted on a piilley, 'a 'strap around the eccentric mean rand tension means between the armaand the strap'.

3AA parallel 'm'otion'drafting-device oi "the pulley and band type including :anohoring means adapted to be attached "to aidrawing board and comprising arms pivoted at adjacent ends, one

of said arms being pivoted at a iree'end to the anchoring means, a 'pa-ir' 'of spaced pulleys in each arm, an endless band passing around each pair 'of pulleys, a 'disc 'ecc'entricall-y 'mounted on a pulley, a ring surrounding the disc and formed with an arm and tension mean-s be'tweenn'the end of the arm onjthe ring and the arm of the drafting 'device.

4'. A parallel motion drafting device of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adiacent ends, one 'of said "arms "being pivoted 'at a tree end t'othe anchoring means, a pair o'f *spaced pulleys in each arm, 'an endless band passing around each pair of pulleys, a disc 'eccentrically mounted *on'a pulley, a ring surrounding the disc, anti-friction means between the ring and the disc, said ring being formedw'ith an arm and tension means between the end of the 'arm on the ring and the arm of the 'drafting'device.

5. A parallel motion drafting 'device of the pulley and band type including anchoring means "adapted "to be attached to'a drawing board and comprising-arms pivoted at adjacent ends, one of said arms rb'eing pivoted at a free end to the anchoring means, "a pair of spaced pulleys'in each arm, an endless band passing around each an of pulleys, a 'disc eccentrically mounted on a pulley, a ring surrounding the disc, the proximate faces of the ring "and disc being formed with raceways and ball bearings between the :raceways, said ring "being formed gang-02o nearest the pulley te th'earm, and coil springs surrounding bers. v

80A"parallel-motiondrawing-device of the pulley and band type including anchoring means-adapted to "be attached to a 'drawing board and comprising arms"-pivoted at adjacent ends, one o'f said-arms be'ing' pivoted at :a free end to the anchoring means,--a' pai-rot spaced pulleys ineach arm, an endless band pa'ssing around each pair of pulleys, eccentric means carried by a pulley, a strap around the eccentric means formed "with a paiir of circumfereritially spaced-ears-and tension means between the arm and the strap'comprising a pair {of spaced frame members, bolts passing through the frame members and' the ears and connec'tingthe irame member remote f-rom t'he pulley' to -the strap, a bracket member carried 'by' the arm, a bolt passing through the f-rame members and the bracket member and connecting the frame" member nearest the pulley to the arm,-:coil springs surrounding the 'bolts between the frame members tension means between the arm andthe strap comprising spaced members, compression means between the members and meansconnecting the member nearest the pulley to the arm and the member remote from the pulley to the strap.

7. A parallel motion drafting devic of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, one of said arms being pivoted at a free end to the anchoring means, a pair of spaced pulleys in each arm, an endless band passing around each pair of pulleys, eccentric means carried by a pulley, a strap around the eccentric means formed with a pair of circumferentially spaced ears and tension means between the arm and the strap comprising a pair of spaced frame members, bolts passing through the frame members and the ears and connecting the frame member remote from the pulley to the strap, a bracket member carried bythe arm, a bolt passing through the frame members andthe bracket member and connecting the frame member and-*means to "adjust the compression on the springs. w

9. Aparal'lel *motion'dratting device of the pub ley and band .-type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacerit ends, one of saidarr'ns being pivoted'at a free 'end to the anchoring means, a'pai-r of spaced pulleys in each .arm, an endless bandpassing around each pair of pulleys, eccentric v means 'carried by' :a pulley, a strap around'the eccentric means formed' with a pair of -circumierentially spaced ears 'and tension 'means betwe'en the arm and the strap-comprising a pair 'of spaced "frame members, bolts passing through the frame members and the ears and connecting the frame-member remote from the pulley to the strap, -'a "bracket member'o'arried by'the arm, "a bolt passing through the frame members and the bracket member and connecting the frame member nearest the pulley to the arm, and coil springs surrounding the bolts between the frame members, saidframe members being formed with seats for the springs.

10. A parallel motion drafting device of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, each arm comprising end members and spaced tubular members extending therebetween, one of said verse member carried 'by the tubular members proximate the end member, eccentric means carried by a. pulley, a strip around the eccentric means and tension means between the arm and the strap comprising spaced members, compression means between the members and means conmeeting the member nearest the pulley to the transverse member and means connecting the member remote from the pulley to the strap.

11.- A parallel motion drafting device of the pulleyand band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, each arm comprising an end member and spaced tubular members extending therebetween, one of said arms being pivoted at a free end to the anchoring means, a pulley in the member of each arm, an endless band 'in the tubular members the bolts between the ffiram'e rmemconnecting the member remote from the pulley to the strap.

12. A parallel motion drafting'device Of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, one of said arms being pivoted at a free end to the anchoring means, a pair of spaced pulleysin each' arm, an endless band passing around each pair of pulleys, a disc eccentrically mounted on a pulley, means to adjust the eccentricity of the disc, a strap around the eccentric means and tension means between the arm and the strap.

13. A parallel motion drafting device of the pulley and band type including anchoring means adapted to be attached to a drawing board and comprising arms pivoted at adjacent ends, one of said arms being pivoted at a free end to the anchoring means, a pair of spaced pulleys in each arm, an endless band passing around each pair of pulleys, eccentric means carried by a pulley in an arm, a strap around the eccentric means and tension means between said arm and the strap.

14. A parallel motion drafting device of the pulleyand band type including anchoring. means adapted to be attached to a drawing board and comprising a pivotally movable arm, a pulley carried thereby and fixed in orientation with respect to the anchoring means, means having a' cam surface relatively fixed eccentrically with reference to the pulley and spring means between the arm and the eccentric means to engage various portions of the said cam surface to counterbalance vthe weight of the arm.

15. In a spring counterbalance for a drafting machine including an anchor member defining a fixed axis pivotally supporting an arm member of a parallel motion mechanism, the combination of: a cam-member secured to said anchor member and defining a circular cam surface eccentrically disposed relative to said fixed axis; means on said member defining a housing directed toward said cam surface; cam engaging means slidably mounted in said housing and engaging said cam surface; and compression spring means in said housing for urging said cam engaging means into pressure engagement with said cam surface.

16. In a spring counterbalance for a drafting machine including an anchor member defining a fixed axis pivotally supporting an arm member of a parallel motion mechanism, the combination of a cam member fixed with respect to said anchor member and defining a cam surface eccentrically disposed relative to said fixed axis, spring means carried by the arm member and cam engaging means actuated by said spring means to engage with the cam member to counterbalance the arm member.

17. In a spring counterbalance for a drafting machine including an anchor member defining a fixed axis pivotally supporting an arm member of a, parallelwmotion mechanism, the combination of a cam member fixed with respect to said anchor member and defining a cam surface eccentrically disposed relative to said fixed axis, said arm member including a housing at least partially surrounding aid cam member, spring means carried by the said housing of said arm member and cam engaging means actuated by said spring means to engage with said cam mem- 40 ber to counterbalance the arm member.

LEENDERT KETTING. 

